How do you find the sum of every number within an array?

Question

For example:

var numbers = [1, 2, 3, 4];

would equal 10.

var temperatures = [100,90,99,80,70,65,30,10];

for (var i = 0; i < temperatures.length; i++) {
  var temp = temperatures[i];
}

I am currently trying to build a function which finds the average of an array.

Answer 1 · 2018-09-30T13:36:32Z

September 30, 2018 1:36pm

There are various ways of doing it. The simplest way that does not rely on any functions or techniques you have likely not come across yet (like reduce) is to loop over the list like this:

var numbers = [1, 2, 3, 4]; // Initialize numbers variable

var sum = 0; // Initialize sum variable
for (var i = 0; i < numbers.length; i++) { // Loop once for each item in the list
    sum += numbers[i]; // Uses the counter of the loop to pull out items from the list
}

console.log(sum); // Will print out 10

Since the counter for the loop (the i variable) will start at 0 and go up by one each time the loop runs it can be used to pull out each item from the list. The first time it runs it will pull out the item at index 0 (the first item), the second time the loop runs it will pull out the item at index 1 (the second item) and so on.

If you are still confused, or feel that my explanation was unclear, then feel free to reply with followup questions. I'll gladly answer anything I can.

Answer 2 · 2018-09-30T13:39:42Z

September 30, 2018 1:39pm

Perfect, completely understand, thanks for your help.

Answer 3 · 2018-09-30T14:19:42Z

September 30, 2018 2:19pm

Hiya there! It can be done in a single line of code with the reduce method in the Array.prototype. Here how it can be done:

const arr = [1, 2, 3, 4, 5, 6];
arr.reduce((num, acc) => num + acc); //21

I hope it helps!

~ Ari ~

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How do you find the sum of every number within an array?

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Ari Misha

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